Due to the heavy increase of mobile broadband usage all over the world, increased capacity in cellular systems are needed. This can be achieved in several ways. One is by increasing the system bandwidth (BW), another approach is to introduce advanced receivers capable of subtracting co-channel interference (in multiple input, multiple output (MIMO) scenarios for instance). Extended BW is already standardized in the Third Generation Partnership Project (3GPP) with dual carrier/carrier aggregation possibilities. However radio spectrum is a scarce resource and hence in some regions it might not be possible to use carrier aggregation. Therefore advanced receivers including interference cancelling or subtraction techniques are also being standardized in 3GPP and will be of large importance in future cellular communications. In fact, receivers capable of carrier aggregation could utilize the excess processing power for interference cancelling purposes in scenarios where a single carrier is used. Hence advanced receiver capability and dual carrier receivers are linked to each other.
Communication directly between wireless radio devices or terminals, so called Device-to Device (D2D) communication, is also important in future wireless networks. D2D communication is characterized by direct communication between two devices without the need for the data to go via a network node. D2D communication might be done using already existing radio access technologies or techniques, such as Bluetooth, or WLAN/WIFI direct, or it might be done by using future network (NW) assisted D2D communication protocols in Long Term Evolution (LTE) communication standards. NW assisted D2D communication has advantages over non-NW assisted D2D in terms of power consumption and spectrum utilization (the NW node decides when to use cellular or D2D communication).
A device connected to an LTE cell receives control information on the physical downlink control channel (PDCCH). Information which it uses to conclude whether it is scheduled in the downlink in the current sub frame. The device attempts to blindly decode multiple PDCCHs in each sub frame and, if successful, the decoded information contains the parameters necessary to receive the data transmission.
However, a significant problem in the interference cancellation scenario, with i.e. an advanced receiver capable to cancel other cell interference is how to obtain information about the scheduled users (i.e. the interferers in neighbouring cells). This knowledge is needed in order to be able to receive the signal from the neighbouring cell for further use in the cancellation process. Blind decoding of the PDCCHs transmitted in the neighbouring cell is typically not feasible since the device is not aware of which devices are connected to the neighbouring cells, making the cancelling process significantly more complex.
Therefore there is a need for method and apparatus facilitating the blind decoding of a control channel in the mobile device in order to enable the device to do advance interference cancelling of signals transmitted from neighbouring cells to neighbouring mobile devices.
FIG. 1 schematically illustrates a prior art scenario. A radio device a is connected to NW node A and a radio device b, which is in proximity to the device a, is connected to NW node B. Both NW nodes A and B use the same carrier frequency (as indicated by the solid arrows for data signal transmissions). Since the devices are close to each other, the signal from NW node B to device b interferes with the reception by device a of the signal from NW node A and vice versa (dashed arrows are indicating the interference). If the device a can receive/detect the device b signal, it is possible for device a to subtract or suppress that interfering signal and improve the signal to interference ratio (SIR) of the wanted received signal from node A. The problem here is that device a needs to be able to detect the interference. The more information received about the interference, the easier the suppression/cancellation is. Several blind detection techniques are known in the art.
WO2013/007491 discloses a method for providing co-channel interference information by a network node by receiving information for at least one user equipment (UE) connected to an adjacent network node, determining a co-channel interference list for user equipment (UE) connected to the network node wherein the co-channel interference list is based on the received information and transmitting the co-channel interference list to a UE connected to the network node. This solution requires fast information exchanges between the network nodes and the information needs to be broadcast (or unicast) from the network node to the UE, which requires spectral resources.